Measuring instrument.



No; 655,276. Patented Aug. 7, |900.

F. SCHRTTKE. MEASUBING INSTRUMENT.

(rApplicatiun led Nov. 18, 1899,)

(No Model.)

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UNITED STATES PATENT EEICE.

FRANZ SCI-IRO'ITKE, OF BERLIN, GERMANY, ASSIGNOR TO THE SIEMENS drIIALSKE ELECTRIC COMPANY OE AMERICA, OF CHICAGO, ILLINOIS.

MEASURING INSTRUMENT.

SPECIFICATION forming part of Letters Patent No. 655,276, dated August7, 1900.

Application iiled November 18,1899. Serial No. 737,433. (No model.)

To all whom, t may concern.-

Be it known that I, FRANZ SCHROTTKE, a subject of the Emperor ofGermany, residing at Berlin, Germany, have invented a certain new anduseful Improvement in Measuring Instruments, (Case No. 255,) of whichthe following is a full, clear, concise, and exact description,reference being had to the accompanying drawings, forming a part of this1o specification.

My invention relates to measuring instruments, and has for its objectthe provision of improved means for measuring the energy of poly-phaseelectric circuits.

Accurately to measure the energy in a threephase circuit it has beennecessary to obtain simultaneous readings of the energy traversing eachcircuit thereof. Itis, however, possible accurately to measure theenergy conzo tained in three-phase circuits also by the use of twoseparate wattmeters by employing the well-known two-wattmeter method. Ifinduction-meters are used or meters which operate through the agency ofa rotating field,

z 5 it is necessary that the magnetic effects due to the current in thepressure-coil be displaced by an angle of ninety degrees from theimpressed pressure which produces them.

It is the prime object of this invention to provide simple means fordisplacing the resultant magnetic effects due to the pressurecoilsninety degrees from their impressed pressures.

Generally speaking, my invention consists 3 5 of means wherein thecurrent traversing one circuit is combined with the geometrical sum ofthe pressures impressed upon two of the circuits of the system.

I will more particularly describe my inven- 4o tion by reference to theaccompanying drawings, in which- Figures 1, 2, and 3 are phase andVector diagrams for illustrating the electrical problems involved, andFig. Llisa diagrammatical arrangement of the preferred embodiment of myinvention.

Similar letters of reference indicate similar parts in the differentviews.

In the following description it will of course 5o be understood that theaddition and subtraction of voltages and currents when out of phase is ageometrical or vector operation and not an arithmetical addition andsubtraction. The energy traversing a three-phase circuit is equal to theproduct of the currents traversing the separate circuits with therespective electromotive forces which produce them. This expression,mathematically expressed, will be Cl/:lileie-eb) i"biee-Q) l-Cieb-evdla(1,) in which the letters a, ib, and te, Fig. 1, represent the currentstraversing the three circuits, and ea, eb, and e0 represent therespective pressures which produce them. By re 65 placing the negativeresultant of two of the currents i., ib by the currents te, or,mathematically expressed,

ic: I @Dfi-ib), we deduce from equation l the fact that the energytraversing the circuit is equal to onethird of the difference betweentwo separate factors in which both factors are equal to the product ofthe currents traversing one of the circuits and three times theelectromotive forceimpressed upon one of the remaining circuits, or,mathematically expressed,

As either of thepressures traversing one `of the circuits is thenegative resultant of the pressures traversing the other circuits, or,mathematically expressed,

it follows that the total energy traversing the circuit may be dividedinto two separate and independent factors, the rst consisting of 9o theproduct between the current traversing one circuit and the geometricalsum of the pressures impressed on the remaining circuits and in whichthe second factor consists of the product of the current traversing oneof; the remaining circuits with the electromotive forces impressed onthe two other circuits, or, mathematically expressed,

azz', [earl-ec] -fib [eb-keel. It is obvious from this equation thatfour readings of a dynamometer are necessary to obtain the total worktraversing the circuit, while only two readings are required if twofields are created, each proportional to two of the pressuresimpressedupon the circuit. In measuring this energy I preferably employ twoseparate induction motor-meters and provide each with two separatefield-coils, each fed by one of the-pressures of the circuit, therebyobtaining a resultant field which is displaced ninety degrees from theresultant of two of the pressures of the circuit.

Referring to Fig. 2, fu, and o2 are two equal factors which aredisplaced from each other by an angle 71. The geometrical sum of thesetwo factors-that is, o, -l- J2- is displaced ninety degrees from thegeometrical difference-that is, vieta-the two factors being equal. Thisprinciple may be applied to the present inventionif the electromotivevforces e.L eb ec are equal. We then obtain the resultthat the energytraversing the circuit is again equal to the difference of the twofactors in which each factor is equal to the product of the currenttraversing one circuitA and the geometrical difference of the pressuresimpressed on twoy of the remaining circuits, or, mathematicallyexpressed,

Each one of the factors contained in this equation can therefore bemeasured by means of induction-meters in which each pressurefield iscreated by means of two separate pressures of a three-phase circuit, oneof the pressures being the pressure across the. circuit the current ofwhich traverses the series coil of one of the instruments, the otherpressure being one of the pressures of one of the circuits which is notincluded therein. Two separate pressu re-coils are therefore required toproduce the resultant pressure-field for eachwat-tmeter. In thepreferred embodiment of the invention I employ two separate pole-piecesfor these coils, so that no divided winding is necessary for either oneof the pole-pieces. The windings or the number of turns contained ineach one of the pressure-coils must be equal if the current traversingthis coil be in phase with its pressure. If the currents t', 2, Fig. 3,are displaced from their respective pressures o, o2 by an angle rp, itis necessary that their strength be varied by means of resistances inorder to obtain a resultant current which is displaced ninety degreesfrom the resultant of the pressures producing it. As the magnetism is inphase with the current, the resul-tant magnetism due to these twoseparatecurrents will be displaced ninety degrees from the geometricalsum of the pressures producing it.

In the preferred embodiment of my invention, Fig. 4, I employ twoinduction-meters d d', each containing two series fields ff and twoshunt pole-piecesg handig 7L'. The series coils of the induction-meter dare traversed by the current i, of one of the circuits. The

Vmgbeing included in the circuit.

current-coils of the meter d' are traversed by the current b in one ofthe remaining circuits. The pressure-coil g of the meter d is fed by thepressure ce, a resistance m being included in the circuit. The othershuntfield h of the meter is fed by means of the pressure @ma resistancem being included in the circuit. The pressure-coil g of the meter d islfed by the pressure eb, a resistance m2 being included in the circuit,Ythe other field h being fed by the pressure ec, a resistance Twomeasurements may thus be performed with one measuring instrument,inasmuch as'the combination of the field g due to the one pressurecoiland the series coil f creates a turning moment, and the combination ofthe pressure in the shunt-coil h with the current in the current-coils fproduces a second turning-.m0- ment. The shunt-fieldsY g and h having adifference of phase are not equal at thesame instant even with an equalnumberof ampere turns in each. The fields g and h will thereforesometimes be closed through the series coilsff; but this is nodisadvantageand will not create any theoretical error, the constant ofthe meter being alone aiected, as the increase of one field g, forinstance, is accompanied bya corresponding decrease of the oppositefield h.

In instruments which employ disks it ispossible to place thepressure-coils, which are fed by separate pressures, onoppositesidesthereof, this being a very advantageous arrange-l ment. Theproportionate change ofthe ampere turns of the two pressure-windings ofthe meter does not materially affect the phase lof the resultant fieldcreated thereby. This is a material advantage, as the sensibility of theinstrument may easily be adjusted to the desired strength withoutmaterially aifectin g the adjustment of the meter. If the instrui menthas not the desired sensibility, -a proportion ate decrease of theresistances included in series with the shunt-fields will increase theampere turns upon each ofthe coils,.andthereby increase the sensibility.If the instrument has reached the desired sensibility, a very slightchange in either one of the resistances in the circuits thereof willreadily adjust the phase displacementof ninety degrees of the resultantfield. The driving moments actuating the moving parts ofthe twomeasuring instruments may be readily obtained from equation 3 and areproportional to the product of the current traversing the series fieldsand the geometricalV difference of the pressures in the ieldcoils,or,math.em atically,

moments, and c1 and c2 the respective constants. If both instruments areadjusted so that the constants cl and c2 are equal, their moving partsmay be mechanically coupled, and I obtain a double induction-meter whoseIIO readings are proportional to the total energy threading thethree-phase circuit. The energy is accurately measured by thisinstrument, even with an inductive loading of either of the legs of thesystem.

I have herein shown and particularly described the preferred embodimentof my invention; but I do not wish to be limited to the precisearrangement shown, and

I claim as new and desire to secure by Letters Patent* l. Thecombination with a polyphase system of electrical distribution, of awattmeter having motive windings comprising series and two sets ofpressure coils, a pressure-coil of one set being connected in parallelwith a pressure-coil of the other set, one terminal of each' of theremaining pressure-coils of each set being connected to the conductor inwhich the series coil of the other set is included, the other terminalbeing connected to one of the remaining conductors of the system,substantially as described.

2. The combination with a polyphase system of electrical distribution,of a wattmeter having motivewindings comprisingseries and two sets ofpressure coils, a pressure-coil of one set being connected in parallelwith a pressure-coil of the other set, one terminal of each of theremaining pressure-coils of each set being connected to the conductor inwhich the series coil of the other set is included, the other terminalbeing connected to one of the remaining conductors of the system, thefirst-aforesaid pressure-coils receiving their pressure from the twoconductors of the circuit which includes the series coils, substantiallyas described.

3. The combination with a polyphase system of electrical distribution,of two electric induction-motors having rotatably-mounted armatures,indicating means adapted to be operated by said armatures, series coilseach included in one of the conductors of the said system in inductiverelation with the said armatures,shuntcoils in inductive relation withthe said armatures,one terminal of each of the said shunt-coils beingconnected to the conductor in which the series coils of the respectivemotor members are included, the other terminal being connected to one ofthe remaining conductors of the system, the said pressure-coils beingconnected in parallel relation, and additional shunt-coils in inductiverelation to the said armatures, each of the latter two shunt-coilsreceiving its pressure from the two conductors of the .system notincluding its corresponding series coil, substantially as described. t

4. The combination with a polyphase system of electrical distribution,of two mechanically-coupled electric inductionmotors, havingrotatably-mounted armatures, series coils each included in one of theconductors of the said system in inductive relation to the saidarmatures, shunt-coils in inductive relation to the said armatures, oneterminal of each of the vsaid shunt-coils being connected to theconductor in which the series coils of the respec FRANZ SCHROTTKEVitnesses HENRY HAsPER, WoLDEMAR HAUPT.

